mtd: spi-nor: Avoid setting SRWD bit in SR if WP# signal not connected

Setting the status register write disable (SRWD) bit in the status
register (SR) with WP# signal of the flash left floating or wrongly tied to
GND (that includes internal pull-downs), will configure the SR permanently
as read-only. If WP# signal is left floating or wrongly tied to GND, avoid
setting SRWD bit while writing the SR during flash protection.

Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@amd.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20230630142233.63585-3-amit.kumar-mahapatra@amd.com
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 5f29fac..434c545 100644 (file)
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -2844,6 +2844,9 @@ static void spi_nor_init_flags(struct spi_nor *nor)
        if (of_property_read_bool(np, "broken-flash-reset"))
                nor->flags |= SNOR_F_BROKEN_RESET;
 
+       if (of_property_read_bool(np, "no-wp"))
+               nor->flags |= SNOR_F_NO_WP;
+
        if (flags & SPI_NOR_SWP_IS_VOLATILE)
                nor->flags |= SNOR_F_SWP_IS_VOLATILE;
 

diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index 4fb5ff0..55b5e7a 100644 (file)
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -132,6 +132,7 @@ enum spi_nor_option_flags {
        SNOR_F_SWP_IS_VOLATILE  = BIT(13),
        SNOR_F_RWW              = BIT(14),
        SNOR_F_ECC              = BIT(15),
+       SNOR_F_NO_WP            = BIT(16),
 };
 
 struct spi_nor_read_command {

diff --git a/drivers/mtd/spi-nor/debugfs.c b/drivers/mtd/spi-nor/debugfs.c
index e11536f..6e163cb 100644 (file)
--- a/drivers/mtd/spi-nor/debugfs.c
+++ b/drivers/mtd/spi-nor/debugfs.c
@@ -27,6 +27,7 @@ static const char *const snor_f_names[] = {
        SNOR_F_NAME(SWP_IS_VOLATILE),
        SNOR_F_NAME(RWW),
        SNOR_F_NAME(ECC),
+       SNOR_F_NAME(NO_WP),
 };
 #undef SNOR_F_NAME
 

diff --git a/drivers/mtd/spi-nor/swp.c b/drivers/mtd/spi-nor/swp.c
index 0ba716e..5ab9d53 100644 (file)
--- a/drivers/mtd/spi-nor/swp.c
+++ b/drivers/mtd/spi-nor/swp.c
@@ -214,8 +214,13 @@ static int spi_nor_sr_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
 
        status_new = (status_old & ~mask & ~tb_mask) | val;
 
-       /* Disallow further writes if WP pin is asserted */
-       status_new |= SR_SRWD;
+       /*
+        * Disallow further writes if WP# pin is neither left floating nor
+        * wrongly tied to GND (that includes internal pull-downs).
+        * WP# pin hard strapped to GND can be a valid use case.
+        */
+       if (!(nor->flags & SNOR_F_NO_WP))
+               status_new |= SR_SRWD;
 
        if (!use_top)
                status_new |= tb_mask;